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        riddles >> general problem-solving / chatting / whatever >> Is it true?
        
(Message started by: BNC on Dec 27^th, 2004, 2:49am)

Title: Is it true?
Post by BNC on Dec 27^th, 2004, 2:49am

This story used to appear in (I think) Borland's C++ help file"

Quote:

True story: 7 Hz is the resonant frequency of a chicken's skull cavity. This was determined empirically in Australia, where a new factory generating 7-Hz tones was located too close to a chicken ranch: When the factory started up, all the chickens died.

I can't find it in any of the "urban legends" sites I know. Does any of you know if it's true or false?

Thanks!

Title: Re: Is it true?
Post by towr on Dec 27^th, 2004, 3:43am

It's doubtfull it's true (haven't checked yet). Infrasound can be dangerous to people and (other) animals, but it would have to be rather loud.
I think 10-15 Hz is about the range where you start feeling ghosts ;)

Title: Re: Is it true?
Post by BNC on Dec 27^th, 2004, 4:44am

I realize it sounds like an urban legend... however it is possible. If chicken skull do have a single resonant frequency, then rather small intensity sound waves may result in a large damage.

The thing is, I'm about to introduce the concept of resonance to my students. It's a "nice" story to tell -- if it's true.

Title: Re: Is it true?
Post by towr on Dec 27^th, 2004, 5:45am

It does have to be high intensity sound. You have to get more energy into it than goes out. That's why you can't break a glass just by singing (another urban legend)
Of course, even though the chickens head may not explode (or be otherwise damaged physically), they may get sick enough to stop eating, or stress out, and die anyway.

Title: Re: Is it true?
Post by John_Gaughan on Dec 29^th, 2004, 11:52am

I play bass guitar, and I can see effects even around 110 Hz ("A" string, two octaves below A440). Random objects in my house will vibrate, enough that living creatures are affected (e.g. my cat will get up and move). If I crank the volume the effects are stronger, but still don't hurt anything. Like towr mentioned, I haven't broken any glasses or dishes or windows or anything, at least not without dropping them ;)

Title: Re: Is it true?
Post by Icarus on Dec 29^th, 2004, 2:16pm

I suspect this is true, to some extent (it may not be true that all the chickens died). But I am sure the deaths were caused by stress effects as towr as mentioned, and not by actual physical damage from the sound.

Title: Re: Is it true?
Post by John_Gaughan on Dec 29^th, 2004, 6:44pm

I think it would probably take at least 100 dB before the sound waves caused physical harm, depending on the exact animal in question. According to Wikipedia (http://en.wikipedia.org/wiki/Decibel), 130 dB is the threshold of pain.

Title: Re: Is it true?
Post by Noke Lieu on Jan 13^th, 2005, 10:30pm

Well, it would have been news to me, literally. That sort of thing would have made the news over here.
As an aside... industrial noise levels are capped at 85dB in most states. Instant stop work at 140dB.
The UNSW (Uni of New South Wales- quite reputable) did s study on development chicken brains that found (http://www3.interscience.wiley.com/cgi-bin/abstract/68502595/ABSTRACT)
Quote:

a biphasic morphology in all chickens with one peak at about 6 Hz and another at 26 Hz.